How much do iPhone 3GS' sell for?

In the UK, and second hand. Wanting to sell mine for a decent price (but not practically give it away ha)

Thanks

200 to 300, 400 at very max

I was selling the same, I bought it off a friend for £80 after my Bold broke. I just got my iPhone 5 and went to sell it to Cex, and because it had a scratch on the back it was classed as 'not working' and £13. Ridiculous? I'd suggest avoiding second hand shops, sell for about £100, alot of people sell 4gs' for £200, so don't overcharge.

It depends how many GB the iPhone is. There are some second hand ones on eBay that are selling for about £80 - £90.